function [p0,k,err,y] = newton(f,df,p0,delta,epsilon,max1) 
%---------------------------------------------------------------------------
%NEWTON   Newton's method is used to locate a root.
% Sample calls
%   [p,k,err,y] = newton('f',df,p0,delta,epsilon,max1)
% Inputs
%   f         name of the function
%   df        name of the function's derivative input
%   p0        starting value
%   delta     convergence tolerance for p0
%   epsilon   convergence tolerance for y0
%   max1      maximum number of iterations
% Return
%   p0        solution: the root
%   k         actual number of iterations
%   err       error estimate in the solution p0
%   y         solution: the function value

%---------------------------------------------------------------------------

for k=1:max1
  p1 = p0 - feval(f,p0)/feval(df,p0);
  err = abs(p1-p0);
  relerr = 2*err/(abs(p1)+delta);
  p0 = p1
  y = feval(f,p0)
  if (err<delta)|(relerr<delta)|(abs(y)<epsilon), break, end
end